In many different applications the visual appearance of such a lighting device is of high importance. This is especially the case in applications where the lighting devices are directly visible such as is often the case with for example chandeliers where the lighting devices are provided in the form of light bulbs. Therefore the construction and design of lighting devices is a very important issue within the field of luminaire design.
A side effect in such lighting devices is that excess heat is produced, especially in high lumen lighting devices. This excess heat must be removed to avoid adverse effects on the lighting device. To remove the excess heat a heat sink is provided. The larger the lumen output of the lighting device the larger the heat sink necessarily becomes. This has the drawback that at least a part, and most often a major part, of the heat sink is visible, which from a user's point of view gives the impression that the lighting device emits light from only a limited part of the surface of the cover element. This is neither practically nor aesthetically satisfactory.
US 2012/0307498 A2 describes one attempt at solving the above problems by providing a LED lighting device comprising a plurality of light sources, a primary heat sink and a secondary heat sink and a globe portion made of glass. The secondary heat sink, which is a metal conductor, is provided in association with the glass globe. The glass globe may be frosted or otherwise light diffusive.
Even if this construction in the case the glass globe is actually frosted or otherwise light diffusive to some extend provides a hiding effect with respect to the secondary heat sink, the secondary heat sink will still be at the least partially visible from a user's point of view.
Therefore, there is a desire and need for providing a lighting device which from a user's point of view emits light from the major part of or even the entire surface of the cover element, in which the excess heat produced is nevertheless removed, even in case of high lumen lighting devices, and which is furthermore versatile in terms of design options.